原题

http://www.codewars.com/kata/find-nth-digit-of-a-number

题目

The function findDigit takes two numbers as input, num and nth. It outputs the nth digit of num (counting from right to left).

• Note
  If num is negative, ignore its sign and treat it as a positive value.
  If nth is not positive, return -1.
  Keep in mind that 42 = 00042. This means that findDigit(42, 5) would return 0.
• Examples

findDigit(5673, 4)     returns 5
findDigit(129, 2)      returns 2
findDigit(-2825, 3)    returns 8
findDigit(-456, 4)     returns 0
findDigit(0, 20)       returns 0
findDigit(65, 0)       returns -1
findDigit(24, -8)      returns -1

分析

解决本问题只需要两步：

1. 把需要判断的位挪到个位(整除)
2. 再把个位数取出(取余)

参考答案

#include <cmath>

using namespace std;

int findDigit(int num, int nth){
    return nth <= 0?-1:int(abs(num)/pow(10,nth-1))%10;
}

说明

其它